• 31-12-2023

Hello everyone I'm opening this thread hoping to help others and also to get help with some of the issues that I'm still facing with my 2006 Audi A6 4F C6 / V6 2.7 - 3.0 TDI BMK BPP engine .
So let's start this long story... I own the car since 7 or 8 years now, and the car drove well for first 2 years ... after which i had to replace the intake manifolds / collector as they worn up to the limit. Since I bought the car, the passenger side door was not opening from outside if locked and unlocked, then the rear drivers door started making the same joke and still have this issue up to date as you will notice below. I also replaced the battery about 4 years, ago as the original one was dead after 14 or 15 years of faithful duty life but i did not registered it in the ECU, as luckily it did not gave any errors (Battery has almost same specs and dimensions as the original one Varta, only 10 amps higher power, as I could not find one with exactly same amps but I don't think that will make a difference as the car starts fine even in cold seasons).
Then two years ago I started notice higher fuel consumption rate and one year ago blue smoke coming out from the rear exhausts, from time to time (especially after driving at low rpm and then accelerating to 2000 - 3000 rpm range especially climbing hills then would go away after couple of rounds of acceleration and then turning back to smoking). Also sometimes I could hear engine head knocking while cold, but no warning lights in dash board, and noticed that these problems were present mostly on cold weather 19 °C - 15°C and below . Six moths ago, finally the first warning light came up ... DPF warning light . At this point I didn't knew anymore what to think, because initially I suspected the injectors that were playing jokes on me, but after this new issue I suspect injectors and DPF particulate filter.
So I'm thinking to replace the DPF and also the dpf differential pressure and temperature sensor and see how the car will run, Beside these issues, engine was running smooth especially on highway and had good mpg too but as soon as I hit the city everything turns into a nightmare. Last couple of months I also noticed that sometimes the engine idles rough and even shakes, like it's almost stalling, while standing still in traffic and idling, so at this point I started scratching my head.
Finally I decided to get a VCDS tool and scan this car to understand what was happening, and I was quite surprised of what i found...
Below are some readings of the full errors scan and Injection system test. But as I'm new to this hope someone can confirm my theory. Can a clogged DPF make the engine choke after 10 - 15 min of idling , low power and high fuel consumption in city causing blue smoke in acceleration and engine head knocking after these readings? Because injectors by me seem to be OK except the fact that 0,40 and 0,80 values are probably due to misfires or bad fuel to air mixture. As the ECU struggles to balance the two banks or is trying to keep alive the engine, injectors go berserk fighting with balancing the combustion cycles and overall power distribution over the right and left bank of the engine compartment ...


Audi a6 2.7 V6 Injector and DPF diagnose and readings
Did some Colored text highlighting on values I retain normal and abnormal but those are not to be taken as granted as expecting opinions.

• 28-01-2024 Update edit:

This month I'll take down the DPF and put on a regenerated one... All parts are ready to be mounted. got the dpf, Screws, gaskets and exhaust mounting kit with pressure sensor pipes. and the DPF temperature lambda sensor.... Now the mechanic will replace them if bad or something brakes while getting out the old DPF. In the meanwhile I've noticed also smoke and soot deposits and traces in the EGR area and also some oil leak under the right intake manifold, that probably was small, since I've replaced the manifolds 3 years ago, but seems to have gotten bigger. Probably the gasket sealing was bad or cooked due to heat . After dpf will be replaced, those oil and gas leaks will be the next concern that I'll have to fix. I'm curious what happened there ... as the manifold was installed with care ... and in time might have caused the air and intake gas leak to expand.
Curious Fact that I also noticed is that, with time the right intake manifold wears out faster than the left one... same thing happened with the original ones... I wonder why but have no clue for now...
Hope that the black smoke trace or deposit on the pipes and intake actuator is not due to an EGR gas pipe leak or something in that area, but because of the oil and air intake leak from that right manifold, which leads me to think that the manifold gasket should be the issue or else there will be another headache for me ... I'll keep updated this topic after I replace the DPF. (Ok Particulate filter replaced and yes, right intake manifold gasket was leaking oil. As for the gas deposits The EGR module had caused the gas leak due to wear and excess pressure inside the EGR cooler, as I discovered later that the EGR Cooler was Full of soot and carbon deposits)
Some would say why replace Dpf... and you're right ... seems like a nonsense but my intuition leads me to think that the engine is having so-called "black death dpf engine" even though it's not giving any errors except the dpf regeneration warning light once in a while, but if the exhaust gas is too smoky (or does no has a loose / free flow) because of the clogged dpf , leads me to think that the engine is sucking in too much soot and exhaust fumes through the egr circuit and brigs them back inside the engine, leading to even more smoke and un-burned gases clogging the exhaust and engine it's self. It's like a vicious circle that leads to engine diseases and failure sooner or later. (New Update: this theory turned to be true as engine revived after the service, also to note is that restricted egr gas flow on the other side can cause the engine to operate at higher temperature, if is obstructed or egr valve is defective, because the EGR gases help lower engine combustion temperature once inside the cylinder )

• 10-04-2024 Update edit:

As I say " better to prevent then cure" problems or diseases, it turned out that replacing the DPF was the right thing to do. Once I've replaced the DPF on my Audi A6 V6 2.7 Tdi already started recover from Illness. After 30 minutes of driving testing and measuring engine performance, the car has already begun to run better. Second day (work travel) 30 min highway to work and 40 min city travel back from work MPG are almost back to normal (Decreased from 9 - 8,2 l/100km to 6,5 - 7 l/100 km) and also noticed less often smoke coming exhaust. Engine sound is also getting better, but still need time to throw out all the deposits and ash accumulated form the old clogged particulate filter.
Rpm, revving up and engine vibration are almost normal. Also torque, power and acceleration stages are almost as responsive as they wore before.
Last remaining minor issues to take care, or wait to go away, are some small downshifting gear hiccups (that my mechanic told me, might come from worn out gearbox struts) and acceleration hesitations from time to time .
Just found some useful tips , thinking back at my strange engine behavior and found that the Common Rail fuel pressure regulating valve might also be faulty as it has exactly same behavior and sound as in the linked video below
I've tested the High Fuel Pressure Valve mounted on the common rail engine rack , but before starting the engine, so would work under stand sill low or no pressure conditions. So as I was thinking that was OK (as it was ticking at 9V battery test ) but I might be wrong ... as it might be worn and does not do the deep loud tick of the piston inside, and instead just does a weak spark-like ticking (just like in the linked video). That probably explains also the constant range or 470 - 482.8 bar pressure in the High Fuel Pressure section of the table (Witch I also thought was OK but apparently is not, seen cases where should variate or decrease under acceleration at around 200 bar , where mine does not ). I suspect clogged, corroded or blocked valve piston of the High Fuel Pressure Valve.
(PS: apparently The high fuel pressure seem to have changed after the DPF replacement and during acceleration pressure increases to 400 - 600 bar and during idle drops down to 200 - 300 wonder if this was related to the clogged filter but as i don't have nominal workload values I'll have to dig into this ... Update After the Egr cooler cleaned, engine sound and fuel rail valve clicking noise are now OK ... almost as it should be . As before AGR and intake cleaning, when I could barely hear it, that was not a good sign... it was too silent probably due to bad readings that the ecu was getting from engine, making the High Fuel Pressure Valve to operate at lower pressures )
Did this inquiry also because I've noticed that while accelerating ( at Warm Engine - in temperature 90°C) at 2000 - 2500 rpm I feel a small vibration in engine compartment like one cylinder is slightly out of phase or almost misfiring . But As I've said I'm awaiting for the engine to clean out the remaining soot that built up inside. Next thing to do, as the 25000 Km service is near to deadline, is to replace filters and engine oil (as to me seems diluted by diesel) and see how things will work out from there.

• 15-08-2024 Update edit:

Car drove well for 2 or 3 weeks but some old problems turned back, and some new ones jumped out of the box. Engine lost some power, almost as turbo or egr valve were not responding adequate so I Took down the entire intake and Egr system, cleaned it all up and replaced the consumed parts like gaskets, EGR module and intake flap mounts and mostly finishing the entire repair story.
Conclusions: While cleaning the entire intake system but even since I've replaced The DPF, I kind of feared that by replacing the DPF, it could partially release the exhaust system and push further, the buildup or accumulated soot, back inside the intake circuit through the EGR, event that inevitably happened.
So Things are starting to make some sense here. After more testing, checking and inspecting the engine I'll try to explain and list down, how I suspect issues started on this engine with all the images, symptoms,and related spare parts list. I will also describe the main cause and factory engineering design flaw that I suspect this engine has and can also be applied to earlier and later models that have similar intake design. Intake Valves, air and EGR gas flow issue inside BPP engine head - Audi A6 3.0 - 2.7 V6 TDI common rail Direct Injection study.

1. Right bank injector seal leak (engine head knock) - Sill to check --->
2. ---> Engine start clogging DPF and EGR with soot ( DPF replaced, EGR cooler cleaned EGR module replaced, EGR valve cleaned but still to be replaced as it was stuck and cleaning and unblocking it did not gave results) - OK --->
3. ---> Intake manifolds excessive wear due to engine overheat caused by injector seal failure that caused bad combustion and excessive exhaust gases and soot (entire Intake Manifolds replaced altogether with the internal swirl flap and one swirl flap actuator ) - OK
4. Air filter box flap defective ( flap or valve membrane not opening) - To be replaced

Problems that the Audi A6 4F C6 / V6 2.7 - 3.0 TDI BMK BPP engine is having:
So...Let's start form the beginning. Initially I noticed that after testing - Intake air and EGR gas flow problem. BPP V6 Common Rail - DPF started to clog, the engine lost some power, smoked from the exhaust and started building up excessive soot deposits on the intake. Beside the engineering flaw that audi made by implementing this Euro4 antipollution system, generally there are various upstream problems that cause malfunctions rather than the soot clogging itself . The only way to prevent this is to detect and fix the problems in a timely manner.
Premises :
If you hear: engine head knocking excessive soot deposits on intake manifolds and valves - a DPF light showing up in dashboard - blue or black exhaust smoke - engine running too lean or rich - engine noise that is too silent or quiet ( low clicking sound from rail valve and injectors) - the usual engine noise under heavy acceleration whooshing hushing or roaring / wrooming sound of the engine under heavy acceleration (referring to the usual sound that the engine should do when it reaches the 3000 - 4000 revs before shifting gear up ) missing or it is not longer there - engine running too lean or rich - excessive soot deposits on intake manifolds and valve stems -exhaust soot from 05 to 1 mm in thickness on the exhaust pipes ,... you should check what may be the cause of this problem, because When the warning lights come on, it is usually a little late, and major repairs and cleaning need to be carried out on this engine.

The 1st Generation V6 engines on Audi A6 2.7 - 3.0 TDI BPP - BMK common problems: Audi A6 bpp clogged engine. EGR problems and Service Protocol: The main problem of this engine is that in case of one or more injector malfunction, excess exhaust gases and soot are sucked back into the engine from the badly burned combustion exhaust gases. What's worse is that since it's a Direct Injection , the intake valves are not cleaned or sprayed , by any kind of additive or diesel lubrication.
Therefore, before / while replacing / removing the DPF or soon after , check the following components : leaky or bad injectors - injector seals or nozzles - cylinder compression - engine oil ( Bad or inadequate engine oil ) - and elongated or stretched timing chain can also be a problem.
- Not to be excluded a bad ecu or electric / electronic problem as piezzo injector current flow should be as following



Long story short , Luckily in my case did not lead to total engine failure, but most of the times, before you decide to buy and replace spare parts, you need to study and understand very well, the symptoms that the engine has in order to get to the root of problem that is causing it.
Also, in this case, the black smoke traces or deposit on the pipes , intake actuator and the EGR module ( OEM : 059131063D ) was due to excessive wear and high gas pressure inside as the Egr valve got stuck with soot. Service Log number 5:

• 26/08 2024 Update edit:

With a cleaned Egr cooler engine runs almost perfect.but while working and after final driving experience I also Noticed carbon deposits on the intake valves (note: that as on this engine the intake valves are actually a direct injection systems design or CRD that never spray the valves with diesel they tend to build up carbon deposits in case of EGR circuit or oil burning malfunction) which I'm thinking to clean with some CRC intake valve cleaner and see how it goes.
Also had a look at engine performance with VCDS and noticed some changes in engine feedback after the repair work I've done , and comply with the reality, but I still have to check some small details and parts such as:
- Injectors 0445115080 that most probable are the root of the problem
- Intake Map sensor 4047024934481 as it might be dirty
- And maf sensor 047026453409

I'm thinking of solving the problem of valve carbon buildup by installing an oil catch canister on the turbo intake return line hose of the PCV valve and perform a cleaning of the intake valves, from time to time, using a DIY intake fuel injector system, until the next inspection of the intake valves. At least this seems to be the safest way.



Final observations notes:
The soot deposit on the exhaust pipe are almost gone, as engine seems to almost have gotten cleaned up and rechecking injectors with VCDS cylinder number 3 injector seem to be slightly jamming - worn or has a leaky washer seal, as value is not out of range, but still higher then others (normal value should be around 0.09 up to 0.34 while number 3 sometimes stays jammed at 0.8 and sometimes even 1.0 - And I doubt that there is a VCDS ecu refresh rate problem).
I've also missed to mention one small detail about rpm's erratic idle that I've noticed my Audi A6 was doing before all other issues started (as I didn't gave much attention to it in the beginning, right before all others problems started, but can come in hand to diagnose or foresee the upcoming issues ) and found on online web search that ( here is a huge detailed story ) there are lots of owners that complain about this problem, but no one managed to solve the mystery. My opinion is that mostly is caused by erratic piezzo injector spray pattern and obstructions of EGR gas flow but most common fault is the injector number 3 on right bank passenger side knocking. Reason might be that looking at the intake design that seems to be the most straight away intake flow of air and gases so it can lead to bad air to diesel mixture inside piston number 3 leading to all kinds problems, but in plain and simple diagnose it's just a irregular gas flow on the intake or injector malfunction and it all reflects on that weak spot cylinder number 3 (in most cases but depending on how the carbon soot has buildup inside the intake manifold and EGR can cause even other cylinders to misbehave ) .
I would also advice not to interfere too much with the vehicles electronics ( such as remapping adapting or modifying the ECU ) and just appeal to this as last resort to solving the issues on this engine model, as most of the times, the malfunctions and faults are mostly due to wear , driving habits and mechanical failures. As the the ECU Engine mapping of the car was made when assembled / produced according to certain parameters, variables or specifications, with wear and time these parameters modify mostly because of mechanical failure such as mechanical parts , valves, gaskets, rubber membranes, seals, plastic hoses or intake obstructions.
Also possible symptoms and noises caused by bad intake air and EGR gas mixture or injectors:

• short acute snoring or clanking rattling noise at low rpm while driving in engine head that suddenly goes away 5 -10 - 15 second -> Possible cause : nickel yttrium oxide or formation of yttrium oxide and nickel oxide deposits on the piezo injector crystals ( " Precursor solutions that are appropriate for SP methods are metal salts (acetates, bromides, chlorides, hydroxides, nitrates, sulphides) dissolved in water or alcohol")
• Cylinder / piston head knocking -> Possible cause: Piezo Injector diesel leak or over-spraying or over fueling diesel inside the cylinder (often mistaken as timing chain rattling)
• Engine Head hissing (very similar to timing chain rattling but more like a hissing noise ) -> Possible cause: injector washer seal blown, melted or cracked.
• Fluctuating or erratic idle, occasional -periodic-sporadic blue smoke from exhaust pipe , irregular acceleration and gear shifting.: bad intake air and EGR gas flow
• Exhaust Smoke blue or black with medium or heavy diesel smell.

In all above, best way of getting to the bottom of the problem causing these noises and symptoms (before changing any parts and wasting money on useless repairs) is to thoroughly scan / check injector readings and clean completely the intake and EGR circuit (egr cooler included) inspecting all parts for signs of wear. Check and clean the intake valves if they present carbon deposits. After having done all this now, you can identify the cylinder and the injector causing this, extract it from the engine and inspect all seals and eventually cylinder and valves using a bore scope.
INJECTOR DIAGNOSE AND READINGS WITH SCAN TOOL advice and hints - The tricky part of finding one or more bad injectors:
VCDS caught the bad injector in cylinder number 3 while driving and cruising on highway and back in city after 30 min drive watching the injection Quantity deviation of all cylinders. Images and readings below explain it all. As I've exhausted all possibilities to back trace the faulty part of the engine responsible for all these erratic irregular engine running and idling problems, the last part to blame were the injectors.
So Why so difficult to find injector malfunction? In my case took me some time because I was quite confident that injectors were fine for the following reasons:

• The diesel filter was changed every 30.000 to 60.000 km and periodically used diesel additives to keep them in good health
• I mostly made Diesel refueling at gas stations that I've retained trustworthy but unfortunately it turns out all these precautions do not help that much at preventing injector failure and copper washers wear sooner or later.

On the other side, hard to detect injector malfunction, in my case, was due to the diagnosing stage that the bad readings were showing up, as injectors were not severely damaged so here are some tips and tricks on how to scan Faulty injectors , that apparently work fine , but not all the time.

1. Run scan when the car did not run for 3 or 4 days. At cold engine to warm-up stage
2. Run scan when engine in temperature. While idling and then at certain RPM's
3. Run scan in winter and summer.
4. Run scan while cursing on a 30 min trip should show up
5. If no bad readings are show up repeat stage 4 scan for 4 or 5 times.

If no bad values are found after all these steps then you can be sure enough that injectors are in good health, Often happens that a failing injector hide bad readings if scan is made only 2 or 3 times, also bad readings are not always concomitant with malfunction symptoms, so don't let yourself get tricked by this fact. Audi a6 V6 injector service repair - Finding the bad injector:
In the readings above, my case, seems like cylinder 3 and 5 have bad values, but not to be taken as granted. number 3 leaking -1.27 and number 5 stuck 1.08.
As injector 3 and 5 ( from image above) are in synchronizing firing order, there is the chance that number 5 is ECU stuck to balance the right and left bank. Most probably 90% injector 3 is bad as I can also hear injector knock on right bank. Once replaced I'll re-scan and check the outcome.

Bad injectors or bad injector seals symptoms, causes and signs on Audi A6:
Repeated / frequent DPF regeneration - Engine head knock or detonation - oil cap blow-by - excess wear or pressure inside the EGR , egr cooler and intake manifolds - excess carbon build up on the intake - High MPG - Sluggish acceleration - Oil dilution - unstable / erratic / juddering or bobbing idle and engine vibrations - excessive soot on intake valves and swirl flaps.- Engine running too rich or too lean - blue smoke from exhaust with smell of diesel - unequal or unbalanced power distribution between right and left bank on v6 engine - Failed dpf regeneration - Engine misfire - Engine hesitation or stumble - Rpm needle bounce - no starting just cranking - difficulty starting the engine - anticipated or unexpected acceleration - sputter when accelerating.

• 15/10 2024 Update edit:

In the meantime new injectors and sealing kit arrives I'll do some in-depth analysis on best practices and advice to extract , replace injectors gone bad and fix the ones that have burned sealing or cause compression issues. As injector related issues, are one of most common problems, on this engine, very precise work is need to be done as injectors are quite tricky to diagnose and fix...
problem must be somewhere somehow related to combustion. Bad combustion = bad gas mileage, bad engine running and bad exhaust gases.
Servicing injectors seem to be most difficult part in fixing up combustion problems but I can only think at the following steps:

• Find the bad injectors
• Thoroughly and carefully clean the injector seat - Inspect injector Port (seat) and hole for cracks , Deformation or scratches
• Inspect parts for eventual signs of wear or breakdown that can help for further diagnose on what could have cause it, such as:

- injector nozzle carbon buildup, oxidation or deformation
- Injector sealing wear tear or burnout
- bore scope cylinder health

• Carefully seat and remount new or refurbished injectors
• Code the new injectors
• Rerun tests and readings looking for signs of malfunction

I'm also thinking that altogether either the rest of the injectors are not at their best as i can see small deviation values on the rest of them also... but not as bad as number 3 and 5, so depending on how engine will run after replacing worst ones , will probably take out the other ones too for cleaning, maintenance and copper seal replacement an visual inspection of the old ones.
Heard voices claiming that.these piezo injectors cannot be refurbished and also not to be tested as traditional ones on engine with return line leak test as they can go bad while testing because the return line must always be under a certain pressure.
Anyway most common are burned copper sealings that lead to compression loss inside cylinder, engine blow by, piston overheating and even blue smoke . Once that blows off, gases escape thru the escape duct, that is cast inside the engine valve head and blown out right above the exhaust manifold. If the escape duct gets clogged or the upper rubber sealing of the injector is blown It can cause crankcase pressure problems leading to possible oil leaks inside the piston from valve stems piston rings or oil vapor on the intake circuit from PCV valve and obviously oil dilution.

AUDI A6 C6 3.0 and 2.7 V6 TDI 05.2004 - 10.2008 BPP engine piezo injector spare part codes:
Also applied to Audi A4 B7 Avant; Audi A6 C6 Avant; Audi A6 C6; Audi A4 B7 Limousine; Audi A4 8h; Audi A6 C6 Allroad quattro
Bosch CRI3 - 16 - OEM 059130277 AJ - 059130277 BB - 059130277 AC can be found refurbished, While the brand new OE 0445115080 injector is mostly made in Turkey. There is also a rotation spare-part code that Bosch delivers under 0 986 435 388

• 15/10 2024 Update edit:

Surprise ... Surprise ... even more discoveries Big mystery, doubts and curiosity on how problems started and what caused this chain of events and failureof parts one by one , unleashing the hole story and nightmares.
All parts arrived so I'm ready to extract the faulty injector, I've started with cylinder number 3 as it seemed to be the worst one, and indeed it stoned me in front of the view I've had .
But ... Before going further I'll list a couple of advises on how and what to do and not to do while extracting an injector.

• If engine warm let it cool down (this will allow the high pressure in the rail decrease avoiding diesel spills)
• Once opened the injector cover and released the bracket DO NOT WIGGLE OR FORCE the injector out with up - down or left - right movements in order to to release and extract it out of the engine (this can lead to injector port deformation )
• Be careful while taking out the injector and unscrewing the injectors holder / bracket as the nut or copper washers can fall inside the camshaft head

In front of this last discovery I have a couple of hypotheses on what could have happened , but awaiting your opinions and questions for more details and hints as the story did not ended here. At least I am at mid way of solving the problem as there's more to discover, and hope this thread is useful to who is having problems similar to mine .
Couple of observations to make :
- While taking off the injector's return line notice that the green/red factory paint sealing was broken or ripped sign of a previous service.
- On the tip of the injector I actually notice a possible tool marking as zoomed in above.
- While extracting the injector was not forced, came out fairly well using an extractor.

Back to injector number 3 here ... As I tested the car engine was running better but was still making jokes ... so i decided to insist as it is a V6 ... on the rest of the other 5 remaining injectors replacing them one by one, each month and as a result I've concluded that:
Most of the Injectors were clogged... out of 6 from visual, ecu data and symptom diagnose results are:
- 1was noisy - 1 had seal leaking oil from valve head inside the injector port and also bent injector or deformed / out of axis injector port (as i struggled a bit to put the new one inside) - 3 had the tip (pintle spay holes) clogged with carbon and - 1 had the injector port hole inside the head slightly oval shaped, but not bad enough to replace the valve head or not to seal properly.
And just wait the story doesn't end here... there's more ! Interesting part is that if I'd had to trust a mechanic I would have blanked my egr and taken off the dpf by now... then remap engine , then replace gear box and who knows what else ... beside injectors maybe even the timing chain ... Probably this is the reason why most of these A6 series are almost gone if not extinct on roads today ... as I'm not seeing them around anymore lately.